The two-riddles post was a success, and while corresponding with Greg Kuperberg he had a riddle for me about dinosaurs, and he agreed I will share it with you.

Right before the Chixculub asteroid hit the earth, there were a variety of mammals and a wide variety of dinosaurs. Both the mammals and the dinosaurs lived in many places, came in many sizes, etc. Why did some of the mammals survive, but none of the dinosaurs did?

A nuch simpler question: Can you answer (without clicking or googeling or so):

How many years did the dinosaurs live? (you know,.. not a single one but them as a whole…) 1 million years, 5 millions, 20 millions, 50 millions, 100 millions?

6 Responses to Greg’s Dinosaurs Riddle

Certainly not! It may sound like a deep philosophical question, but it is actually not all that deep and not all that philosophical. It is a good student question in evolutionary biology. The answer is that evolutionary biology is a theory of statistical drift and not a theory of imperatives or virtue.

Of course the question of belief and interpretation comes up a lot in evolutionary biology, at least when learning it. Why is it ever important to believe anything in science? When are interpretations important? The basic reason is that you will get more work done if you believe X, Y, or Z, or if you accept a particular interpretation. The correct role of belief or advocacy in science is that it is practical advice for learning a subject and doing better research. Otherwise scientists shouldn’t care what you believe, because science should not be like religion or politics.

With respect to that role of belief, it only obfuscates matters to think of any extinct species as a loser, or to conclude that any animal morally “should” propagate its genes. It is like saying that forwarded e-mail is “winning” e-mail, while e-mail that is only sent once is “losing” e-mail. Such a moral judgment is a distraction from understanding e-mail.

As an Earth Science / Math double major, these are relevant to my interests 🙂

Well, obviously, the first part depends on what classification system you use. Since the trend these days is to use phylogenetic trees, the dinosaurs have not gone extinct, merely the non-avian dinosaurs, which is a paraphyletic group. In other words, only some mammals survived, and only some dinosaurs survived. In yet another set of words, the question is predicated on an assumption that is false.

For the second part, I guess I’d go with from the Permian-Triassic boundary to present. So, on the order 250 million years. But it’s a bit lame to ask without being more specific about the tree you’re using, and how the clade of dinosaurs is defined on that tree.

For the final bit: All men are mortal, and all species go extinct. Taxa are successful while they are extant, and the fact that they went extinct doesn’t make them “losers”, just like the fact that George Washington is dead doesn’t make him a loser.

Dear Greg, thanks for the riddle and the comment which provide a lot of food for thought. At least the combination “dinosaurs+losers” is not new. (try google images for a surprising image-winner) and look also at this:

Your second paragraph clearly goes beyond the narrow question of dinosurs and the wide question of beliefs, interpretation, and advocacy in science is very interesting. I also share your overall sentiments towards the dinosaurs. Maybe it is insensitive to refer to them as losers but were they?

Jan De Lanoy is of course correct. It has long been suspected, and is by now well established, that birds are more closely related to a Tyrannosaurus Rex than a Tyrannosaurus Rex is to a Stegosaurus. Since the latter two are both commonly recognized as dinosaurs, the only basis for saying that birds are not dinosaurs is that they are not extinct. In other words, dinosaurs became extinct only by definition.

It’s also true that a duck is about as closely related to a Tyrannosaurus Rex as a kangaroo is to an elephant. The latter two are both mammals, so the former two should go into some comparable category.

It is worth examining what the definition of a dinosaur is or what it should be. A reasonable definition could be “a related group of animals that contributed most of the fossils of large land animals during the Mesozoic period”. Again, there is no way to exclude birds unless you explicitly add extinction to the definition. Of course, as Jan also says, there is the question of where you should cut of the family tree of animals to have the right size of related group. One definition is to take all animals that are more closely related to a Tyrannosaurus Rex than they are are to a crocodile. This definition is not unreasonable, and it is the working definition, but it is also based on which animals did not go extinct.

It’s a great example of how your thinking can go wrong from a bad definition. It’s not just a question of semantics; it has implications for understanding dinosaur fossils and guessing the parts that were not fossilized. One of the traits to identify dinosaurs is that they have birds’ feet. For instance in this photograph, the resemblance is unmistakable, but you might well not think of it if you do not know that birds are dinosaurs:

Another issue is feathers. It’s now pretty well established that many or the dinosaurs in the movies Jurassic Park and King Kong should have been feathered. (But there were also dinosaurs that were probably not feathered.) For instance Jurassic Park had velociraptors and these are now known to have had feathers and maybe even vestigial wings.

Also concerning the other question that you introduced:

Maybe it is insensitive to refer to them as losers but were they?

At the moment I think of dinosaurs as a very interesting topic, but other than that I have no particular sentiment towards them. It’s not a question of animal rights. So I don’t think that it is particularly insensitive to call them winners or losers, just irrelevant. Natural selection is just a statistical phenomenon and it’s a distraction to interpret it with value judgments.

For instance, consider a creek in a place such as California that had a gold rush. Many such creeks once had many gold nuggets. But now the gold nuggets are extinct in many of these creek beds, while silicate rocks are still abundant. Should we therefore say that silicate rocks are “winners” and gold rocks are “losers”? It would be silly for two reasons. First, because rocks have no imperative to survive in a creek bed; it’s just a descriptive fact that the bed is made of those rocks that were not removed from it. Second, because if you did want a value judgment, the useful one would be the opposite, that gold nuggets are winners because you can sell them.

Of course many popular science articles have fatuous statements like “survival is a game of luck and skill”, which is in the title of the article that you linked. The articles have these statements because they sound enlightening, even though they’re actually not. The statement goes wrong at the fourth word. Survival isn’t a game at all! Survival of one animal could be viewed as a game, in the sense that animals evolved to want to survive. But animals have no material interest in the survival of their genes, they just want to stay alive to eat, have sex, and maintain their social relations (if they are social animals). After all, we’re animals and that’s what we want. Most people do not live to propagate their genes as widely as possible; why should they?

In fact, genetic propagation is a hopelessly contradictory objective for individual animals, because every animal has genes with opposing selection pressures. Some of your genes would want you to assassinate your brothers, so that you can have children with their widows. But you also have other genes that your brothers share, and these genes want you to cooperate with your relatives.